The annual prediction from Kathy Mathews, Western Carolina University’s fearless fall foliage forecaster, should make chamber of commerce officials across the Western North Carolina mountains happy this year.

That’s because Mathews is calling for an excellent fall color show, thanks in large part to weather conditions over the spring and summer.

“2011 should prove to be an excellent year for fall color,” said Mathews, WCU associate professor of biology specializing in plant systematics. “While heavy spring rain is generally not a good sign for fall color, records indicate that rainfall was slightly below normal for March, average for April and May, and slightly below normal for June and July, as gardeners struggled to keep their crops watered,” she said. “These conditions actually are promising for good development of leaf color in September and October.”

In addition, mid-August brought a respite from the hot temperatures of June and July, another good sign of vibrant leaf color during autumn, she said.

Mathews believes that the formation of higher levels of yellow, orange and red pigments in the leaves seems to correlate with dry weather throughout the year. The drier the climate, the more brilliant the fall leaves tend to be, she said.

Of course, when it comes to forecasting the vibrancy of the fall color season, just as with forecasting the weather, there are no guarantees. Cloud cover and ample rainfall in the weeks ahead could mute the color show, Mathews said.

“Anyone remembering the last two years may have noticed a shortage of brilliant red leaves in our area, which could be blamed on cloudy weather and rain during the fall,” she said. “Hurricane season also can be hard to predict as far as bringing rain to the mountains, but if we see cool and sunny weather, we can expect nice red color to develop this year.”

Tropical storm Lee dropped heavy rains on Western North Carolina, which could affect fall colors in the mountains, Mathews said.

The cooler temperatures of autumn contribute to the decomposition of chlorophyll, the chemical that gives leaves their green color in spring and summer. As chlorophyll breaks down, yellow pigments – always present in the leaves, but masked by the green of chlorophyll – are revealed, and new red pigments are produced.

Depending upon the timing of the first frost, the peak of fall color should arrive during the second week of October in the higher elevations, and during the third week of October in the mid-elevations, Mathews said.

“Early November can bring surprising bursts of color, too, particularly between 2,500 and 3,000 feet as the oaks peak out in oranges and reds while other trees’ colors are lingering,” she said. “Those planning leafpeeping vacations should have a fairly broad window of time in which to choose for viewing excellent color change in the mountains this year.”

The color change should begin at the higher mountain elevations in late September and continue through mid-November in the lower levels of WNC.

“Look for the earliest color change to take place on the sourwoods and dogwoods, which both turn red, as well as the tulip poplars, which become yellow but tend to turn brown early,” Mathews said. “Colorful maples, with hues of red, orange and yellow, and birches, which turn yellow, bring us into the peak period. Finally, oaks turn orange and red to round out the later color change in the season.”

Sweet birches and tulip poplars are already starting to turn yellow in the mid-elevations around Cullowhee, which is a normal occurrence for this time of year, she said.

“Over the month of September, the color change should continue and spread. Expect buckeyes to give pops of orange early, as well. Maples will add more yellows, oranges and reds as they gradually change in late September, and sourwoods should turn a beautiful, deep red,” Mathews said.